<< Lets say I have just read a book. ... the book is in the public domain.
<< ... later I have adapted the book .... and someday I find out Paramount
is doing
<< an adaptation themselves.
<< Is there anything I could do to avoid this scenario; to protect myself
from other
<< screenwriters/producers/studios in adapting the same book? >>

No. Public Domain is just that, the domain of the public = everyone. All you
own are the rights to YOUR adaptation of the material.

Was there anything unique in the way you adapted/ltreated the material that
was NOT part of the original? Is Paramount using this same "gimmick" (for
lack of a better word.)? And if so, did they have the opportunity to read
your screenplay?

If the answer to all of the above is yes, then you better get a lawyer, a
good one! If not, then, "Oh, well! Them's the breaks!"

A lot of people read the same classic books you know. How many adaptations
have there been of Kipling's Jungle Books, or Mark Twain's Huck Finn stories.
How 'bout the Shakespeare fellow! He's gotta lot o' coverage over the
years, don't ya' think!!!